This invention relates to a heat sink for a Positive Temperature Coefficient (PTC) heating element and a PTC heating member including such a heat sink. This invention also relates to a method for forming such a PTC heating member, and a method of securing such a PTC heating member to an electric appliance.
PTC heating members are now used in a large variety of electrical appliances, e.g. electric hair styling apparatus, hair straightening apparatus, and facial steamers. Such PTC heating members are provided with a heat sink usually made of a hollow body extruded section composed of a metal, e.g. aluminium. The hollow body extruded section includes two oppositely-facing and generally parallel inner surfaces which are brought into contact with a PTC heating element which includes a PTC pellet or stone, upon deformation of the extruded section. The PTC pellet is electrically linked with an electricity supply, e.g. via two electric wires. The PTC pellet will generate heat upon passing of electricity. The heat so generated by the PTC pellet is transferred to the heat sink for appropriate use, e.g. for onward transfer to a heating surface of an electrical appliance.
European Patent Document No. EP 0 573 691 A discloses a method of producing a PTC heating element. The teaching of this prior art document is incorporated by reference herein. According to this method, the extruded section has a base face on which two webs are provided. Before pressing, the webs stand approximately perpendicular to the plane of the base face, and the webs are connected to a cover face via sections which are curved outward in an approximately U-shaped to semi-circular manner. The extruded section is deformed in such a manner that the radius of curvature of the curved sections is reduced, that the webs are inclined outward relative to the perpendicular by an angle, and that the cover face is brought into contact with the PTC element.
One drawback associated with such prior art heat sinks and PTC heating members made thereof is that such are not suitable for use when the heating element is to be housed in a cylindrical cavity, since the curved sections will be wider after deformation. In addition, the PTC heating members are also required to be assembled to the heating surface of the electrical appliance, which adds to the production procedure, and thus the cost.
It is thus an object of the present invention to provide a heat sink for a PTC heating element, a PTC heating member including such a heat sink, and a method of forming such a heating member, in which the aforesaid shortcomings are mitigated, or at least to provide useful alternatives to the public.
It is also an object of the present invention to provide a method of assembling a PTC heating member to an electrical appliance in which the aforementioned shortcoming is mitigated, or at least to provide a useful alternative to the public.
According to a first aspect of the present invention, there is provided a heat sink for a PTC heating element, said heat sink including a first end, a second end, and a pair of webs extending from said second end towards said first end, wherein each of said webs is connected to the first end via a respective curved section, and wherein said curved section is inward of the respective web.
According to a second aspect of the present invention, there is provided a PTC heating member including a heat sink fixedly secured with a PTC heating element, wherein said heat sink includes a first end, a second end, and a pair of webs extending from said second end towards said first end, wherein each of said webs is connected to the first end via a curved section, and wherein said curved section is inward of the respective web.
According to a third aspect of the present invention, there is provided a method of forming a PTC heating member, including the steps of (a) providing a heat sink with a first end, a second end, and a pair of webs extending from said second end towards said first end, wherein each of said webs is connected to the first end via a respective curved section, and wherein said curved section is inward of the respective web; (b) providing a PTC heating element in a cavity of said heat sink; and (c) deforming said heat sink to secure said PTC heating element with said heat sink.
According to a fourth aspect of the present invention, there is provided a method of assembling a PTC heating member to a heating surface of an electrical appliance, including the steps of (a) providing a PTC heating member including a heat sink fixedly secured with a PTC pellet; (b) loosely engaging said PTC heating member with said heating surface; and (c) deforming said heat sink or said heating surface to secure said PTC heating member with said heating surface.
According to a fifth aspect of the present invention, there is provided a method of assembling a heat sink and a PTC heating member to a heating surface of an electrical appliance, including the steps of (a) providing a heat sink; (b) providing a PTC pellet in a cavity of said heat sink; (c) loosely engaging said heat sink with said heating surface; and (d) deforming said heat sink or said heating surface to secure said PTC pellet, said heat sink and said heating surface with one another.
According to a sixth aspect of the present invention, there is provided a method of assembling a PTC heating member to a heating surface of an electrical appliance, including the steps of (a) providing a PTC heating member including a heat sink fixedly secured with a PTC pellet; (b) abutting said PTC heating member with a side of said heating surface; and (c) biasing said PTC heating member towards said side of said heating surface.